The goal of this project is to design a microfluidic system to synthesize monodispersed nanoparticles. Two microreactors are designed for controlled synthesis of monodisperse nanoparticles. Our first microreactor works by mixing two reagents inside a droplet to synthesize nanoparticles whereas the second microreactor is designed to achieve monodispersity by having thermally isolated zones for nucleation and growth processes and incorporating a two phase flow system to assure uniform reaction conditions. This reactor is fabricated in silicon and it is capable of handling high temperature and high pressure reactions.